Male blackburnian warblers are easily identified by their bright orange throat, breast and forehead. They have a black crown and cheeks and are noted for their two white wing bars and white spots on the outer tail feathers. Blackburnian warblers have a mostly black back, wings, and tail. There are black streaks on mostly white sides and flanks. The lower breast and stomach is slightly orange, fading to white towards the tail.
Females are much less colorful than males. Females have a pale orange to yellow faces and breasts, with brownish crowns, cheeks, and wings. There are two bars of white on the wings. Females also have white bellies and undertail coverts with grayish streaks on the sides and flanks. Juvenile blackburnian warblers look similar to females.
Blackburnian warblers are, on average, 13 cm in length with a wingspan of 21 cm. Like most warblers, they have small, flattened, short bills, and have thin, black legs with 3 toes in front and one in back. (Morse, 1994; Sibley, et al., 2001)
Blackburnian warblers inhabit North and South America from southeast Canada to Peru. They are commonly found throughout southeast Canada, from Alberta into the Great Lake areas to Newfoundland and into the Appalachians as far south as Georgia during the summer season. However, during migration, this species is seen throughout the eastern coast of North America and as far west as Oklahoma. Most migrate over the Gulf of Mexico; however, some fly over the eastern coast of Texas. During the winter they can be found in Costa Rica, Panama, and into Peru. (Morse, 1994; Rappole, 1995)
Blackburnian warblers live and breed in forests during the summer. They prefer pine forests, but can be found in spruce trees or hemlocks. In any forest type in their summer range, blackburnian warblers are most active foraging and vocalizing in pines. They prefer the upper third of tree canopies in dense, mature forests. During the winter they are found in humid, mountain forests from Panama into South America. They may also be found in South American coffee plantations. (Greenberg, 1979; Lawrence, 1953; Morse, 1967; Young, et al., 2005; Zerda Lerner and Stauffer, 1998)
Male blackburnian warblers attract their mates by singing from tree tops. When a potential mate comes close, males flick their tail and peck at the branch. Males defend their mate from other males by flicking their tail, pecking at branches, and occasionally fighting. Blackburnian warblers, like other songbirds, are monogamous which means that one male and one female pair together to breed and raise young. (Lawrence, 1953; Nice, 1926)
Blackburnian warblers typically nest in the higher canopy of the tallest trees. Their nests usually consist of twigs and attached by spider silk, while the inside is lined with dead pine needles and grasses in the shape of a small cup. They build the nest away from the tree trunk and hidden in the leaves. Females are the primary builders and will take 3 to 6 days to build nests. They start building nests close to the time they lay eggs. They typically breed every year between May and July, and lay 1 clutch of 4 to 5 eggs. The eggs hatch in about 2 weeks and the young fledge (can fly and leave the nest) between 2 and 4 weeks. Blackburnian warblers can reproduce when they are 1 to 2 years old. (Lawrence, 1953; Nice, 1926)
Only female blackburnian warblers incubate the nest. Males will bring food to the incubating females who spends most of their time on the nest, keeping the eggs warm. The newly hatched chicks are featherless, cannot open their eyes, and cannot move. This is called "altricial". These helpless chicks need constant care from their parents. Both males and females feed the young but females more so than males. They feed the young every 10 to 20 minutes. The female continues to keep the young warm until they grow their own feathers. After 2 to 4 weeks, the young chicks are learning to fly and are able to leave the nest or "fledge". Both parents continue to care for the chicks after they have left the nest. It takes several months before the young can survive without help from their parents. (Lawrence, 1953; Morse, 1994; Nice, 1926)
Blackburnian warblers live in the wild for a average of 3 to 6 years. The primary cause of death is not surviving through migration. Migration is a long, dangerous journey and most birds fly non-stop over the Gulf of Mexico. Birds that have not stored enough fat or that encounter bad weather may not survive migration. The oldest blackburnian warbler was 8 years and 2 months old. Researchers banded the bird in Minnesota and caught it again 8 years later. Blackburnian warblers are not kept in captivity. (Dunn and Garrett, 1997; Elphick, et al., 2001; Morse, 1994; "Reference Atlas to the Birds of North America", 2003)
Blackburnian warblers usually fly in flocks with many other species. Typically there are 1 to 2 blackburnian warblers per flock, but there can be as many as 7. They are not very social with each other or other species unless they are foraging nearby. Blackburnian warblers are active during the day, and are most active at dawn and dusk. Many closely related warblers prefer to forage in pine trees, just like blackburnian warblers. To make sure each species has enough food, each species forages in a certain section of a tree. Blackburnian warblers forage and nest in the upper canopy and will build their nests in the outer tree branches. Other warblers forage and nest in lower parts of trees. This way, many warbler species can survive in the same habitat without competing with each other.
Blackburnian warblers migrate long distances in spring and fall. In the spring, they fly north to North America from their wintering habitats in South America. After they breed in the summer, blackburnian warblers fly south again in the fall. (Lawrence, 1953; MacArthur, 1958; Morse, 1994)
Blackburnian warblers sing mostly at dusk and dawn. Males use songs to attract mates and advertise territory boundaries. Males are usually stationary, perched at the tops of tall trees when singing. They have two distinct, high-pitched song types, occasionally alternating them during breeding season. They are often seen flicking their tails and pecking at branches while singing. They chirp twice, and repeat these chirps frequently throughout aggressive encounters with other males. Females rarely sing, but produce chips and chirps to communicate with mates or their young. Like all birds, blackburnian warblers perceive their environments through the senses of sight, touch, sound, smell, and taste. (Morse, 1967; Morse, 1989)
Blackburnian warblers are insectivores and forage during the day. These warblers forage by "gleaning" leaves, which means they take insects off of leaves or other parts of a tree. They may hover in mid air to snatch insects from under leaves. They do not forage on the ground. They feed on caterpillars, mayflies, mosquitos, gnats, spiders, and other small invertebrates. (Crawford and Jennings, 1989; Lawrence, 1953; Morse, 1994)
Blackburnian warblers are typically preyed on by larger birds of prey and some mammals. Most predation is on eggs, hatchlings, and fledglings, or on adults as they watch and defend nests. The most common predators are sharp-shinned hawks, Cooper's hawks, red squirrels and blue jays. (Lawrence, 1953; Morse, 1994)
Blackburnian warblers are known for their increased presence during spruce budworm breakouts. In times when populations of these insects are high, blackburnian warblers flourish from increased food abundance. Survival rates and nesting success increase during these times. These warblers are also well-known for their ability to co-exist with many other warbler species in the same habitat. This is accomplished by each warbler species foraging and nesting in a particular section of the forest so that there is little competition. Blackburnian warblers forage and breed in the highest part of the forest canopy. They often share habitat with Cape May warblers, yellow-rumped warblers, black-throated green warblers and bay-breasted warblers.
Blackburnian warblers are used as hosts by feather mites and lice. (Betts, et al., 2006; Betts, et al., 2007; Crawford and Jennings, 1989; Morse, 1994; Peters, 1936; Schulte, et al., 2005; Zerda Lerner and Stauffer, 1998)
There is no known negative impact of blackburnian warblers on humans.
Blackburnian warblers are very habitat selective and prefer large areas of mixed forests and undisturbed, mature pine forests. Surveyors use this species to study the ecology and effect of forest fragmentation by timber harvesting. They are also important for controlling spruce budworm outbreaks by eating large numbers of these insects. This helps the local spruce trees, as large numbers of budworms can cause significant damage to these trees. (Betts, et al., 2006; Betts, et al., 2007; Crawford and Jennings, 1989; Schulte, et al., 2005; Zerda Lerner and Stauffer, 1998)
Currently, blackburnian warbler populations are not considered threatened. They have a large population size that inhabits a large geographic range. However, wintering habitats in South America are rapidly declining due to deforestation, conversion of forests to agricultural fields, or urbanization. Blackburnian warblers are very sensitive to forest fragmentation because they prefer large patches of undisturbed, mature forest. As migratory birds, blackburnian warblers are protected under the United States Migratory Bird Act. Blackburnian warblers are abundant in the northern parts of Michigan. (Morse, 1994)
Reese Clark (author), Radford University, Rachelle Sterling (editor), Special Projects, Karen Powers (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.
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